People with asthma, chronic obstructive pulmonary disease and other breathing disorders need fast relief when their airways tighten up. Unfortunately, the most commonly used medication has obnoxious side effects. But scientists recently discovered that a bitter taste can be a more effective treatment—and now they know why. The work is published in PLoS Biology. [Cheng-Hai Zhang et al., The Cellular and Molecular Basis of Bitter Tastant-Induced Bronchodilation]

When an asthma attack hits, the airway shrinks and makes breathing difficult. To keep air flowing, the sufferer must take medication to relax the passage's muscles and open it back up. But a couple years ago, researchers discovered airways contain bitter taste receptors like the ones on the tongue. After exposure to bitter substances, the receptors can expand the airway more quickly and more effectively than the most commonly used treatment.

Researchers examined airway tissue to learn why bitterness makes the muscles relax. During an asthma attack, calcium flows into the cells of the airway and contributes to muscle contraction. But bitter substances block the channels that allow calcium into cells, which relaxes the tightened tissue. And that's the opposite of a bitter pill.